[boschshc] Code Enhancements (#14667)

[boschshc] Code Enhancements (#14667)

* [boschshc] Code Enhancements

This commit fixes several compiler warnings as well as several
Checkstyle, FindBugs, PMD and Sonar issues.

* instantiate loggers consistently
* add missing logger calls
* add chained exceptions to logger calls
* provide central Gson instance that does not serialize or deserialize
loggers
* avoid catching NullPointerExceptions
* extract methods where cyclomatic complexity was too high
* remove unnecessary null check in combination with instanceof
* rename local variables that shadow fields
* add missing @NonNull and @Nullable annotations

Signed-off-by: David Pace <dev@davidpace.de>